Microwave matching devices



D ec. 24, 1957 D. B. HAAGENSEN MICROWAVE MATCHING DEVICES Filed June 29, 1954 W .Q h m .l n l\ n o ,F u. mi! .//f//l/l//l////////////////f/f//l//////////////////An \N United States Patent() MICROWAVE MATCHING DEVICES Duaney B. Haagensen, Wayland, Mass., assignor to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application lune 29, 1954Serial No. 440,100`

7 Claims. (Cl. 219.-10g51) This invention relates. to a.high.frequency matching device and particularly to matching microwave energy to an external mass for the purposefofdheatingsaid external mass.

This invention discloses a method of using microwave energy for heating purposes. The transfer of energy takes place by radiation between a coil, acting asa coaxial shield, and an external mass which is placed-in close proximity to said coil. Since any two turns of said coil, when placed in a traveling wave, have a differenceof potential, there is produced a voltage gradient between anytwo turns ofl said coil. The external mass being placed in close promixity to this coil is therefore affected by this voltage gradient, resulting in an internal stress in the molecular structure of the external mass. lt is this stress produced by the coil that achieves the desired heating eiect.

Further objects and advantages of this invention will be apparent as the description progresses, reference being made to the accompanying drawings, in which:

Fig. l is a cross-section view of an embodiment of the invention in the form of the microwave matching device for heating liquids;

Fig. 2 is a cross-sectional view of a microwave matching device showing a shorted plug termination; and

Fig. 3 is a graph of the standing wave ratio in a transmission line using the microwave matching device illustrated in Fig. 1 and Fig. 2.

Referring now to Fig. l, there is shown a wave guide in the form of a coaxial cable in an application for heating liquids and a method for placing said liquids in proximity to the microwave matching device.

The outer conductor 11 of coaxial cable 10 is attached to coupling 12 forming an electrical bond to the outer conductor 11. Coil 13 is soldered to coupling 12 to continue the electrical connection and is wound on dielectric support 14 for mechanical strength and terminated by a soldered connection to coupling 15. Dielectric support 14, which is preferably constructed of glass, is sealed to couplings 12 and 15 for purposes of mechanical strength and also for adapting the matching device to a pressurized system. Termination takes place in a flat line termination device 16, as shown.

An inner conductor 17 is centrally located in the glass support 14 by means of suitable locating plugs 18. For purposes of illustration, inner conductor 17 is shown as a continuation of coaxial cable 10. It is apparent that for wave guide applications, persons skilled in the art could construct a suitable probe and connect said probe to inner conductor 17, terminating inner conductor 17 in the flat line termination device 16, as shown.

Fig. l illustrates an application for the heating of liquids as a method of further explaining the invention. Casing 19 with a suitable intake 20 and exhause 21, for the liquid to be heated, is placed around the microwave matching device as indicated. The coaxial cable 10 is then excited by a suitable high frequency generator, thereby causing the inner conductor 17 to conduct the microwave energy. As the microwave energy in the form of a wave moves Parenteanec. 24, 1957 along the inner conductor 17, a voltage is developed across eachturn-of the coil 13. Therefore, at any particular time there isa different voltage on each turn which, in turn, develops a voltage gradient between turns. The actual heat transfer isdetermined by the electrical matching desired which is a function of size of wire, number of turns, and method of winding coil 13.

eierriug now toFig. 2, there is shown a special application for the microwave matching device using a shorted plug 15l instead of coupling 15. The constructionshown in Fig. 2 is similar to that used in Fig. l, with the exception that shorted plug 151 is threaded into inner conductor 171 to accomplish the termination. The shorted plug 151 is used to illustrateanother method of terminating the matching device for special applications. To use the shorted plug 151 termination method, there must always bean external mass or load for coil 131 to radiate energy into; otherwise, reflected waves may cause damage to the high frequency generator. l

Referring ynow to Fig. 3, there is illustrated a graph showing theabsorptionof energy in an external load for both a tlat line termination curve A as illustrated in Fig. 1 and a shortedl plug termination curve B as illustrated in Fig. 2. It will be'noted that for both methods of termination there is approximately 99 percent energy absorption by the external load, the result being that, in either case, a relatively constant absorption of the microwave energy takes place. Therefore, it can be seen that regardless of the termination used, the transfer of energy to the external mass is maintained at a high level, thereby preventing high standing waves.

This completes the description of the embodiment of the invention illustrated herein. However, many modications thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this invention. For example, coaxial cable 10 can be replaced with a wave guide and coil 13 can be constructed of various shapes, sizes and materials, depending on the heating effect desired. For a system having a constantly present load, the flat line terminating device 16 may be substituted by a shorting plug 151 as shown in Fig. 2. Accordingly, it is desired that this invention not be limited to the particular details of the embodiment disclosed herein, except as defined by the appended claims.

What is claimed is:

1. A system using microwave energy for heating a liquid mass comprising an energy radiating means, coupling means for connecting a source of microwave energy to said energy radiating means, terminating means for artitically terminating said energy radiating means, and means for maintaining said liquid mass in close proximity to said energy radiating means, said microwave energy directly heating said liquid mass.

2. A system using microwave energy for heating a liquid mass comprising a coil surrounding an energy carrying conductor for radiating said microwave energy into said liquid mass, coupling means for connecting a source of microwave energy to said energy radiating means, terminating means for artificially terminating said energy radiating means, and means for maintaining said liquid mass in close promixity to said energy radiating means, said microwave energy directly heating said liquid mass.

3. A system using microwave energy for heating a liquid mass comprising a coil surrounding an energy carrying conductor for radiating said microwave energy into said liquid mass, a wave guide coupling means for connecting a source of microwave energy to said radiating means, terminating means for artificially terminating said energy radiating means, and means for maintaining said liquid mass in close proximity to said energy radiating means, said microwave energy directly heating said liquid mass.

4. A system using microwave energy for heating a liquid mass comprising a coil surrounding an energy carrying conductor for radiating said microwave energy into said liquid mass, a coaxial cable coupling means comprising a means for connecting the center conductor of said coaxial cable to said energy carrying conductor and the outer conductor of said coaxial cable to said coil, terminating means for artiiicially terminating said energy radiating means, and means for maintaining said liquid mass in close proximity to said energy radiating means. said microwave energy directly heating said liquid mass.

5. A system using microwave energy for heating a liquid mass comprising a coil mounted on a dielectric support surrounding an energy carrying conductor, said coil being adapted to radiate energy to said external liquid mass, wave guide coupling means for connecting a source of microwave energy to said coil, said coil electrically connected to said wave-guide coupling means, terminating means for artificially terminating said coil, and means for maintaining said liquid mass in close proximity to said energy radiating means, said microwave energy directly heating said liquid mass.

6. A system using microwave energy for heating a liquid mass comprising a coil mounted on a dielectric support surrounding an energy carrying conductor, said coil being adapted to radiate energy to said external mass, wave guide coupling means for connecting a source of microwave energy to said coil, said coil electrically connected to said wave-guide coupling means, terminating means for artificially terminating said coil7 and a casing surrounding said energy radiating means, said casing having openings to receive and exhaust said liquid mass held in close proximity to said energy radiating means, said microwave energy directly heating said liquid mass.

7. A system using microwave energy for heating a liquid mass comprising a coil mounted on a dielectric support surrounding an energy carrying conductor, said coil being adapted to radiate energy to said external liquid mass, wave guide coupling means for connecting a source of microwave energy to said coil, said coil electrically connected to said wave guide coupling means, lat line terminating means for artitically terminating said coil, and a casing surrounding said energy radiating means, said casing having openings to receive and exhaust said liquid mass held in close proximity to said energy radiating means, said microwave energy directly heating said liquid mass.

References Cited in the le of this patent UNITED STATES PATENTS 2,294,881 Alford Sept. 8, 1942 2,399,930 Keister May 7, 1946 2,448,044 OVrebo Aug. 3l, 1948 2,556,642 Bird June 12, 1951 2,633,532 Sichak Mar. 31, 1953 2,718,580 Shirley Sept. 2G, 1955 2,738,406 Zaleski Mar. 13, 1956 2,752,572 Bird et al June 26, 1956 

